1. Field of the Invention
The present invention relates to an image forming apparatus, a post-processing apparatus, and an image forming control method and a program for implementing the method, and more particularly, to an image forming apparatus to which a post-processing apparatus can be attached that controls the sheet conveying speed in accordance with sheet thickness, a post-processing apparatus attached to the image forming apparatus, an image forming control method applied to the image forming apparatus, and a program for causing a computer to perform the image forming control method.
2. Description of the Related Art
Conventionally, image forming apparatuses such as copiers include sheet-type setting means provided in a sheet supply cassette for receiving recording sheets (for example see Japanese Laid-Open Patent Publication (Kokai) No. H07-112834) or setting keys provided on an operation unit for entering sheet types (for example see Japanese Laid-Open Patent Publication (Kokai) No. H08-305210), so that the type of sheets loaded in a sheet supply cassette may be set. There has also been known to carry out control in accordance with the set sheet type to prevent special sheets from being fed unnecessarily, change the speed at which recording sheets are fed from a sheet supply cassette, or change the fixing speed during image formation.
For a post-processing apparatus, attached to an image forming apparatus, for performing a process of sorting sheet bundles and a process of stapling each sorted sheet bundle, there is a demand that the apparatus be capable of performing such processes to any types of sheets discharged from the image forming apparatus. On the other hand, types of sheets handled by image forming apparatuses are increasing, and the capability of image formation on thicker sheets is especially demanded.
For size reduction of a post-processing apparatus, it is effective to bend a conveying path in the apparatus, however, the load applied on a driving system when a sheet is conveyed along the bent conveying path is much greater for a thick sheet than an ordinary sheet. Therefore, in a post-processing apparatus having a bent conveying path, control must be made for causing the driving system to change the torque in accordance with sheet thickness.
However, there is a problem that the optimum torque control cannot be achieved in the post-processing apparatus because the type (thickness) of sheet, which is setting information for each individual sheet feed cassette in the conventional image forming apparatuses, is effective in controlling the image forming apparatus but not necessarily effective in controlling the post-processing apparatus.